Desenvolvimento e validação de uma metodologia eletroanalítica para determinação do inseticida thiobel 500 utilizando o eletrodo de carbono vítreo

Abstract

The indiscriminate use of pesticides has become a problem related to public health, due to the exposure of a large number of people to these products, in addition to being considered one of the main causes of contamination of soil and surface and groundwater. Thiobel 500 is a contact and ingestion insecticide / fungicide, from the chemical group carbamate, used in several cultures. This work aims to evaluate the performance of the vitreous carbon electrode in determining the Thiobel 500, through the study of chemical and voltammetric parameters with the aid of cyclic voltammetry and square wave voltammetry. In addition, the study of the figures of merit is presented, in order to validate the proposed methodology for determining the insecticide. Cyclic voltammetry allowed the determination of the best potential range for determining Thiobel 500, which was from +1.0 V to +1.4 V, through which the acetate buffer with pH 4.5 was also defined as a parameter for determining the insecticide . From the study of the scanning speed, in cyclic voltammetry, it was possible to observe that the nature of the electrode process of Thiobel 500 on the surface of the glassy carbon electrode is controlled by a process of diffusion of the electroactive species of the solution to the electrode surface, which was confirmed in the frequency study using square wave voltammetry. The best parameters defined in the study of square wave voltammetry, for the determination of the insecticide, were: frequency of 60 Hz, amplitude of 60 mV, potential increase of 5 mV, pre-concentration potential of +0.9 V and time pre-concentration of 60 s. From the optimization of these parameters, the study of the concentration of the insecticide was carried out, which allowed the obtainment of a calibration curve for the quantification of the insecticide with linear behavior and coefficient of determination of 0.99596. The study of the figures of merit allowed obtaining the LD of 0.0403 ppm, LQ of 0.1343 ppm. The accuracy of the analytical signal was evaluated by repeatability and reproducibility for a 5 ppm solution of Thiobel 500, obtaining a coefficient of variation of 2.14 and 3.41%, respectively. The apparent recovery of the insecticide was evaluated using the standard addition method, in two samples of tap water, obtaining recovery values of 102.82% and 101.71%. The obtained values demonstrate the feasibility of using the vitreous carbon electrode for electrochemical determination of the insecticide Thiobel 500.